Short-circuiting device



Nov. 26, 1929. J. 0. KARLE SHORT GIRCUITING DEVICE Filed Aug. 15, 1927 R O N E v m ATTORNEY WITNESSE l. I.

Patented Nov. 26, 1929 FFlff.

JOHN D. KARLE, OF ROSELLE PARK, NEVT JERSEY, ASSIGITOR T0 DIEI'IL lYiANUFAC- TUBING COMPANY, OF ELIZABETH, NIEIVV JERSEY, A CORPORATION 615 NEW JERSEY SHORT-CIRGUITING DEVICE Application filed August 15, 1927.

In certain types of motors, more particularly in single-phase repulsion-induction motors, a commutator is used for starting purposes only; the commutator being shortcircuited when the motor reaches a predetermined speed to convert the rotor winding into the equivalent of a squirrel-cage winding.

An object of the present invention is to provide an automatic commutator shortcircuiting device of simplified construction which is efiicient and reliable in operation and in which the wear is evenly distributed and the tendency toward pitting or corrosion of the contact surfaces is effectively controlled.

To the attainment of the ends in view, the motor-shaft has fixed thereto, adjacent the commutator, a carier-member formed with a plurality of radial chambers in which are housed centrifugal weights. Mounted to slide and rotateon and relative to the motor-shaft is a follower-disk having a conical rim or flange overhanging said chambers and hence adapted to be engaged and shifted endwise of the motor-shaft by said weights when the latter move outwardly under centrifugal force. The follower-disk carries a commutator short-circuiting disk which is pressed against the ends of the commutator segments. A recovery-spring shifts the followerand contact-disks away from the commutator when the motor is stopped.

A feature of the invention resides in the 3; means provided to favor creepage of the foldrag on the follower :lisk so that its inertia Serial No. 212,866.

tive to the motor-shaft when the motor is starter The arrz ngemcnt of the weights in radial chambers at right angles to the shaft reduces the side wail friction to a minimum and enables the weights to work freely in their guideways. The device is exceedingly simple in that it comprises, merely, the chambered member, the weights, the followerand contact-members and the recovery-spring. The chambered member may, if desired, be formed with fan-blades at one side of and projecting outwardly beyond the flange of the follow-erdl k to ventilate the motor.

in the accompanying drawings, Fig. 1 is a longitudinal section of a motor embodying the invention. Fig. 2 is a transverse sectional view of the weight-carrying member. F 3 is a sectional view of the device longi tudinally of the motor-shaft in commutator short-circuiting position, and Fig. 4 shows a modification of the weight-carrying member.

in the preferred embodiment of the invention illustrated, 1 represents an enclosed motor frame having end-bonncts 2, 3, with intake and discharge ventilating openi l, 5, respectively, and bearings 6, 6, motor-shaft 7 carrying the usual rotor armature 8 including the commutator Fixed to the shaft 7 between the commutator v 9 and the bearing 6 is the weight-carrying member 10 formed with three radially disposed cylindrical chambers 11 at right angles to the shaft 7 and spaced 120 apart. Slidably fitted within the chambers 11 are the cylindrical centrifugal weights 12 having their outer end edges beveled or coned at 13. Slidably mounted on the shaft 7 and free to rotate relative to the latter is the followerdisk 14 having a tubular hub 15 and a conical rim or flange 16 which overhangs the outer e; "ls of the chambers 11 in position to be engaged by the conical outer ends 13 of the we its 12. Riveted to the inner face of the folk .ver-disk l i is the contact disk 1'? which is radially slotted to form contact teeth 18 adapted to be pre. sed against the ends of the commutator segments 9. Surrounding the hub 15 and motor-shaft 7 is the recoveryspring 19 which yieldingly urges the follower-member 14 and contact-disk 17 toward the chambered member 10, the latter being formed with a thrust-bearing shoulder 20 closely adjacent shaft 7 to reduce to a minimum the frictional drag of the member 10 upon the follower-disk 14. Also, to further reduce the frictional drag in question, the weights 12 and flange 16 are arranged to be initially out of working engagement as shown at 21, Fig. 1.

lVhen the motor is started, the inertia of the disks 14 and 17 sufficiently overbalances the reduced frictional drag to cause a momentary slippage of such disks circularly of the shaft 7, thus repeatedly changing the relation of the contact-disk 17 and commutater circularly of the shaft 7 and effectively controlling any tendency of the contact sur faces to pit corrode or become irregular. As the motor approaches running speed the centrifugal force of the weights applied to the conical flange 16 moves the contact-disk against the end face of the commutator and short-circuits the latter, as shown in Fig. 3. This slippage also effectively distributes the wear of the weights 12 upon the conical flange 16 which latter becomes nicely polished in use. Further, the slippage in question appears to be present at the instant contact of the disk 17 with the commutator is established and to persist momentarily, thus effecting a circular wiping action of the disk 17 upon the commutator and maintaining clean contact surfaces. Still further, the cylindrical weights turn in the chambers 11 and effect an even distribution of the wear upon their conical ends.

The member 10 may be formed at one side of the flange 16 with fan-blades 22 projecting outwardly beyond said flange and serving to ventilate the motor.

The weight-carrying member may also be made in the form of a spider 10, Fig. 4, having three legs 23 formed with chambers 11' for the weights 12. The weights are preferably provided with air holes 24 to prevent suctional retardation of the outward movement of the weights in the chambers 11. The device functions entirely independently of the direction of rotation of the motorshaft.

The invention is not to be understood as limited to the details of construction shown and described as they may obviously be variously modified within the spirit and scope of the invention.

Having thus set forth the nature of the invention, what I claim herein is:

1. In an electric motor having a commutator, the combination with the motor-shaft, of a member fixed to rotate with said shaft and formed with a plurality of radial chambers at right angles to the latter, centrifugal weights mounted in and movable lengthwise of said chambers, a follower-disk free to slide and rotate on and relative to said shaft and formed at its periphery with an uninterrupted conical flange overhanging the outer ends of said chambers, a commutator short-circuiting contact-disk carried by said follower-disk, and a spring constantly urging said follower and contact members away from said commutator and toward said chamber member.

2. In an electric motor having a commutator, the combination with the motor-shaft, of a member fixed to rotate with said shaft and formed with a plurality of radially disposed cylindrical chambers at right angles to said shaft, cylindrical weights slidably disposed in said chambers and having conical outer ends, a follower-disk free to slide and rotate on and relative to said shaft and formed at its periphery with an uninterrupted conical flange overhanging the conical ends of said weights, a commutator shortcircuiting contact-disk carried by said follower-disk, and a spring constantly urging said followerand contact-disks away from said commutator and toward said chambered member.

In testimony whereof, I have signed my name to this specification.

JOHN D. KARLE. 

